Business Central runs on the phone app with the same data and a layout built for it. Approving a purchase order on the train is the usual reason to install it.
Install Dynamics 365 Business Central from the app store, sign in with your work account, and you get a phone-shaped client: role centre cues, lists in a card layout (the "brick"), records with the fields grouped for small screens. Approvers use it for Requests to Approve; field staff for item lookups, stock by location and customer details; anyone with a camera can attach a photo to a record. Barcode scanning in item lookups works with the phone camera.
It respects your role and permissions, so a Team Member sees what they would see anywhere. If a page looks odd on the phone, that is a design choice the developer can fix (page design).
